The Boeing Company has patented the use of carbon nanotubes for structural health monitoring of composites used in aircraft structures. This technology will greatly reduce the risk of an in-flight failure caused by structural degradation of aircraft.
A paper-thin carbon-nanotube film that can heat and solidify the composite materials used in aircraft wings and fuselages, without the need for massive industrial ovens. found about a 1000-fold difference in energy used for curing, resulting in a 50% cost reduction in the final production part.
As different composites require different temperatures in order to fuse, the researchers also tested how hot the CNT film could actually get before it failed. The team found that the film’s failure point was at more than 537 °C. In comparison, some of the highest temperature aerospace polymers require temperatures up to 399 °C in order to solidify.
“We can process at those temperatures, which means there’s no composite we can’t process”
In experiments to test the material's strength, the team found that, compared with existing composite materials, the stitched composites were 30 percent stronger, withstanding greater forces before breaking apart.
Airplane skins are composed of composite materials made up of layers of carbon fibers held together by polymer glue. They can fail when the glue cracks and the fibers come apart, and reinforcing them is tricky. Using pins and stitching might seem like a good idea, but this can pierce and weaken the carbon layers. Researchers led by Brian Wardle, an assistant professor of aeronautics and astronautics at MIT, have now strengthened these advanced aerospace materials with what they call “nanostitching.” Rows of carbon nanotubes perpendicular to the carbon microfibers fill the spaces between them, reinforcing the fiber layers without piercing them.
According to theoretical work to be published by the MIT group in the Journal of Composite Materials, these materials are not only 10 times stronger than those that don’t contain nanotubes, but they are also more than one million times more electrically conductive, which suggests that they might protect aircraft from lightning strikes.